Integrating Plaid with TypeScript

At Ness, we integrated Plaid to streamline onboarding for our consumer credit card platform. The integration reduced onboarding time by 50%, but getting it right required careful attention to TypeScript types and error handling.

Why Plaid?

Plaid provides a unified API for connecting to thousands of financial institutions. Instead of building integrations with each bank, we use Plaid's API to access account data, transaction history, and identity verification.

The TypeScript Advantage

Plaid's TypeScript SDK provides excellent type safety:

import { PlaidApi, PlaidEnvironments, AccountsGetRequest } from 'plaid';

const client = new PlaidApi({
  basePath: PlaidEnvironments.sandbox,
  baseOptions: {
    headers: {
      'PLAID-CLIENT-ID': process.env.PLAID_CLIENT_ID,
      'PLAID-SECRET': process.env.PLAID_SECRET,
    },
  },
});

async function getAccounts(accessToken: string) {
  const request: AccountsGetRequest = {
    access_token: accessToken,
  };
  
  const response = await client.accountsGet(request);
  return response.data.accounts;
}

Error Handling

Plaid uses specific error codes that we need to handle:

try {
  const accounts = await getAccounts(accessToken);
} catch (error) {
  if (error.response?.data?.error_code === 'ITEM_LOGIN_REQUIRED') {
    // Re-authenticate the user
    return redirectToPlaidLink();
  }
  // Handle other errors
}

Security Considerations

• Never store Plaid access tokens in plain text
• Use environment variables for credentials
• Implement proper token rotation
• Log access but don't log sensitive data
• Follow PCI compliance guidelines

The User Experience

The Plaid Link flow is straightforward:

1. User clicks "Connect Bank"
2. Plaid Link modal opens
3. User selects their bank and logs in
4. We receive an access token
5. We can now fetch account data

Results

• 50% reduction in onboarding time
• Higher conversion rates
• Better user experience
• Reduced support tickets

Lessons Learned

1. Test thoroughly in sandbox before production
2. Handle all error cases gracefully
3. Provide clear user messaging
4. Monitor API usage and costs
5. Keep SDK updated

Plaid integration was a game-changer for our onboarding flow.